Mercury cathode electrolytic cells



July 14, 1964 w. c. GARDINER MERCURY CATHODE ELECTROLYTIC CELLS FiledDec. 4, 1961 @EEEEW INVENIOR.

WILLIAM C.GARD|NER By K" W AGENT United States Patent 3,140,991 MERCURYCATHODE ELECTROLYTIC CELLS William C. Gardiner, Darien, Conn, assignorto Olin Mathieson Chemical Corporation, a corporation of Virginia FiledDec. 4, 1961, Ser. No. 156,574 2 Claims. (Cl. 204-219) This inventionrelates to electrolytic cells for the electrolysis of aqueous solutions.The invention more particularly relates to a new method for supportingthe aiibdes in horizontal mercury cells. Previously anodes have beensupported on a rigid frame work resting on the cell walls or outsidecell structure. Examples of other previous modes of supporting anodesare described in US. Patents 2,328,665 and 2,627,501. See alsoIndustrial and Engineering Chemistry, 153 (vol. 45, No. 9), pages1824-1835. The use of the anode support of the present invention onother cells of similar construction is also included within the scope ofthis invention. Horizontal mercury cells usually consist of an enclosed,elongated trough sloping slightly towards one end. The cathode is aflowing layer of mercury which is introduced at the higher end of thecell and flows along the bottom of the cell toward the lower end. Theanodes are generally composed of rectangular blocks of graphitesuspended from conductive lead-ins, for example, graphite or protectedcopper tubes or rods, in such a manner that the bottom of the graphiteanode is spaced a short distance above the flowing mercury cathode. Thebottom and sides of the trough are generally steel with a corrosionresistant hard rubber lining on the sides and under the cover. Concrete,stone or other non-conducting material may also be used for the sides.The lining may comprise concrete which is further coated with resin, orhas natural stone set in the concrete lining.

In the operation of this type of cell the electrolyte, which may bebrine or an aqueous solution of any electrolyte which upon electrolyticdecomposition will give the products desired, is introduced at the upperend of the cell and flows toward the lower end of the cell. For example,a solution of sodium chloride may be electrolyzed in such a cell.Electric current passes through the solution between the anodes and themercury cathode. When sodium chloride is the electrolyte, chlorine isformed at the anodes and passes to the top of the cell and out throughan opening in the cell cover which is provided for this purpose. Sodiumis formed at the cathode as an amalgam with the mercury cathode. Thesodium amalgam is withdrawn at the lower end of the cell, cycled to adecomposer packed with graphite where it is contacted with water to formsodium hydroxide, hydrogen and mercury. The mercury is recycled to thecell for reuse as the cathode. It will be understood that otherelectrolytes, such as potassium chloride, barium chloride, lithiumchloride, sodium sulfate and the like may also be electrolyzed in such acell.

In cells of this type the distance between the graphite anodes and themercury cathode is very important. This distance should be as small aspossible to reduce consumption of energy but if this distance is toosmall, secondary reactions take place, particularly the direct attack ofsodium amalgam by chlorine bubbles. The graphite anodes are generallysuspended by attaching them to lead-ins in turn extending through thecover of the cell and suspended from a structure above the cell cover.Each graphite anode is thus supported at a proper distance from thecathode. The cell cover is usually a steel plate covered with rubber andsufliciently strong to support the anodes and the electrical connectionsthereto. Stoneware or hard rubber covers are sometimes used but cathodeis determined by the way in which the cover fits on the cell and theadjustment of the anodes in the cell cover.

In operation the graphite anodes are consumed thereby increasing thedistance between the anodes and cathode and resulting in reduced energyefiiciency. To maintain the proper distance or spacing between anodesand cathodes it is necessary in this type of prior art apparatus toadjust each anode individually. Another disadvantage is that lifting ofthe cover of the cell for inspection or repair moves all the anodes anddisturbs their adjustment.

Explosions resulting from a combination of electrolytic product gasesoccasionally occur in cells of this type with improperly adjusted anodesas well as in electrolytic cells of other types with consequent damageto the cover for the cell and complete disarrangement of the anodes aswell as possible danger to operating personnel in the cell room.

Attempts have been made to solve the problem of anode to cathode spacingby providing strips or shims between the cover and the sides of thecell. These strips or shims were removed after a certain amount ofconsumption of the anodes had taken place to lower the cell cover andthereby reduce the spacing between the anodes and the cathode. However,accurate adjustment by such a method was not possible. In the mostcommonly used prior art construction the anodes are individuallyattached to the cover of the cell which rests on the side walls of thecell trough and are individually adjustable thereon.

One of the objects of this invention is to provide a combination bus barand anode support for supporting the anodes of a mercury cathode celland permitting adjustment of the spacing between the anodes and theoathode, at the same time supplying current to the anodes.

Another object of this invention is to provide a simplified support forthe anodes of an electrolytic cell which will permit easy adjustment ofthe distance between the anodes and the cathodes.

Another object of this invention is to provide a support for the anodesof an electrolytic cell which will allow simultaneous adjustment ofseveral anodes.

Various other objects and advantages of the invention will appear in thecourse of the following description.

These objects are accomplished and the disadvantages of the prior artstructures are overcome by the use of the present invention.

The invention thus comprises apparatus for electrolyzing conductivesolutions which comprises an elongated inclined trough, a perforated,self-supporting cover over the trough, fixed upright members, transverseelectrically conductive metallic channel-shaped members resting on saidupright members, anode assemblies suspended from said transversemembers, adjustable means to maintain the anode assemblies at aspecified height above the bottom of said trough, a mercury cathodeflowing over the bottom of said trough and means for imposing anelectric current on said anodes and cathode.

The transverse channel-shaped members of this invention providestructural strength to support the anodes without significant deflectionand they maintain their position in use. Anodes once adjusted remain inthe same fixed position until readjusted. All the anodes suspended fromone bus bar usually wear away at the bottom at 7 approximately the samerate, even though the rate may rially reduced. However, individualanodes can be adjusted when necessary.

The transverse channel-shaped members also serve as bus bars to carrythe current to the anodes. Appropriately they are of electricallyconductive metals including particularly copper, aluminum, silver, andalloys containing at least about 60 percent thereof. Most of the commonbrasses contain about 60 percent or more of copper.

The dimensions of the bus bar-support are not critical but depend on thewidth of the cell, the number and weight of the anode assembliessupported thereon and the structural strength and electricalconductivity of the metal. For supporting three to five anode assembliesin a four foot width cell, a copper channel is suitably about 5 to 8inches in width, having 2 to 4 inch flanges and a thickness of about to/2 inch. The bus bar-supports are suitably dimensioned to carry both themechanical and electrical load.

In the attached figure, 11 is the combination copper bus feed bar andanode support. It is a copper channel closed by a copper plate 12 silverbrazed at one end of the channel. To end plate 12 is connected aflexible copper connector 13 which in turn is connected to a bus bar(not shown) carrying the current to the anodes. Flexible connector 13 isconnected to the plate 12 by bolt 14 and nut 15. Channel 11 is drilledwith holes at suitable spacings to receive anode lead-ins 16 and withholes near the ends of the channel to receive jacking screws 17. Thechannel is supported on jacking screws 17 by adjusting nuts 18 by whichthe distance of the channel above the cell cover can be adjusted. Thejacking screws are attached to cell cover 19 by screwing them into nuts20 welded to the cell cover.

Lead-in 16 is attached at its lower end to anode 21 by means of leadbutton 22. The lead-in is tinned at its lower end and held in positionin a mold which is then filled by molten lead. The lead-in 16advantageously has drilled holes near the lower end. The holes in thelower end of the lead-in 16 are filled and covered by the lead affordingfirm support. The lead button is machined, threaded and fitted intocorresponding threads in a recess in the top of the graphite anode. Agasket 23 of rubber is placed around the lead-in in contact with thelead button and top of the anode and then protective sleeve 24 islowered into place. It is protected by another rubber gasket 25 coveringits upper end and nut 26 is tightened to hold the sleeve in place,surrounding the lead-in and separated therefrom by an annular space.

The anode assembly is suspended from the bus bar and supporting channel11 by lower lead-in nut 27 and upper lead-in nut 28 both threaded onlead-in 16 and together locking the anode assembly in its properelevation with respect to cell bottom 29. The aperture in cell cover 19through which the anode lead-in and its surrounding sleeve 24 aresuspended is closed by means of flexible rubber boot 30. The boot 30 issealed against sleeve 24 by clamp 31 held by screw 32. Boot 30 at itslower edge is held tightly against cell cover lining 33 which is turnedthrough the aperture and lies against the top of the cell cover. Clamp34 maintains the seal in position. Boot 30 thus closes the aperturethrough the cell cover 19 and prevents the escape of cell gas whileallowing vertical adjustment of the anode with respect to bottom 29 byadjusting nuts 27 and 28.

Anodes 21 are suspended in theelectrolyzer chamber of the mercury cellconsisting of cell bottom 29 and side channels 35. The side channels 35are lined with hard rubber coating 36. A strip of soft rubber 37 liesbetween rubber lining 36 and cell bottom 29 While another strip of softrubber 3S lies between rubber coating 36 and lining 33 of cell cover 19.

Side channels 35 are held in place by bolts 39 and nuts 4- 40 extendingthrough the flanges of the channel and through the cell bottom. Sidechannels 35 are sealed to top 19 by means of C-clamps (not shown) spacedat suitable intervals along the side of the cell cover 19. The cellrests on transverse I-beams 41 and longitudinal I-beams 42.

Example A battery of mercury cathode cells was constructed for achlorine-caustic plane. Each cell was about 4 /2 feet wide by about 40feet long and contained anodes supported on 40 four foot bus feedchannels of copper.

Each channel supported four anodes, 12 inches on centers and rantransversely of the cell. Longitudinally channels were spaced 12 incheson centers. The anodes were 11% x11% x4 inch blocks of graphite. Eachchannel was 7 x 3% x /8 inchthick drilled through the web to receive theanode lead-ins. These were locked into place with a nut above and onebelow the channel on threads on each lead-in. The channels weresimilarly locked in place on threaded jacking screws at each end of thechannel. The jacking screws were attached to the cell cover by nutswelded to the cover. Current was supplied to the anodes by flexiblecopper connectors attached to an end plate of copper silver-brazed toclose one end of each channel. The circuit was closed by supplyingcurrent to the cell bottom.

In use each cell was supplied with brine and mercury at its upper endand depleted brine, amalgam and chlorine was removed from its lower end.The amalgam was decomposed to form aqueous caustic and the mercury wasreturned to the cell. Depleted brine was dechlorinated, resaturated,purified and returned to the cell. In the course of several monthsoperation, adjustment of the height of the anodes above the mercurycathode was greatly simplified. Usually each group of four anodes wassatisfactorily adjusted by means of the nuts on the jacking screwswithout any change in the nuts on the individual lead-ins. Onlyoccasionally was it necessary to adjust an individual anode.

What is claimed is:

1. In an apparatus for electrolyzing conductive solutions comprising anelongated inclined trough, a perforated, self-supporting cover over thetrough, anodes adjustably suspended through the perforations in saidcover at a specified height above the bottom of said trough, a mercurycathode flowing overthe bottom of said trough and means for imposing anelectric current on said anodes and cathode, the improvement in themeans of suspension of said anodes and in the means for conducting theelectric current to said anodes consisting of transverse, electricallyconductive, metallic channel-shaped members resting adjustably onupright members located above the sides of said trough, the webs of saidchannel-shaped members arranged horizontally with the flanges vertical,perforations in said webs for supporting said anodes di rectly from saidchannel-shaped members, perforations near the ends of saidchannel-shaped members for receiving said upright members and electricalcurrent carrying means attached to said channel-shaped members.

2. The improvement of claim 1 in which said transverse, electricallyconductive, metallic channel-shaped members are composed of a metalcontaining at least 60 percent of an element selected from the groupconsisting of copper, silver and aluminum.

References Cited in the file of this patent UNITED STATES PATENTS2,599,363 Bennett et al. June 3, 1952 2,627,501 Gardiner Feb. 3, 19532,958,635 De Nora Nov. 1, 1960 FOREIGN PATENTS 985,185 France July 16,1951

1. IN AN APPARATUS FOR ELECTROLYZING CONDUCTIVE SOLUTIONS COMPRISING ANELONGATED INCLINED TROUGH, A PERFORATED, SELF-SUPPORTING COVER OVER THETROUGH, ANODES ADJUSTABLY SUSPENDED THROUGH THE PERFORATIONS IN SAIDCOVER AT A SPECIFIED HEIGHT ABOVE THE BOTTOM OF SAID TROUGH, A MERCURYCATHODE FLOWING OVER THE BOTTOM OF SAID TROUGH AND MEANS FOR IMPOSING ANELECTRIC CURRENT ON SAID ANODES AND CATHODE, THE IMPROVEMENT IN THEMEANS OF SUSPENSION OF SAID ANODES AND IN THE MEANS FOR CONDUCTING THEELECTRIC CURRENT TO SAID ANODES CONSISTING OF TRANSVERSE, ELECTRICALLYCONDUCTIVE, METALLIC CHANNEL-SHAPED MEMBERS RESTING ADJUSTABLY ONUPRIGHT MEMBERS LOCATED ABOVE THE SIDES OF SAID TROUGH. THE WEBS OF SAIDCHANNEL-SHAPED MEMBERS ARRANGED HORIZONTALLY WITH THE FLANGES VERTICAL,PERFORATIONS IN SAID WEBS FOR SUPPORTING SAID ANODES DIRECTLY FROM SAIDCHANNEL-SHAPED MEMBERS, PERFORATIONS NEAR THE ENDS OF SAIDCHANNEL-SHAPED MEMBERS FOR RECEIVING SAID UPRIGHT MEMBERS AND ELECTRICALCURRENT CARRYING MEANS ATTACHED TO SAID CHANNEL-SHAPED MEMBERS.